Information storage medium, information reproduction apparatus, information reproduction method, and information recording method

ABSTRACT

An information storage medium according to an aspect of this invention comprises a rewritable area, the rewritable area comprises a user area to store user data, and a defect management area to store defect management information used to manage defective areas on the rewritable area, the defect management area comprises first and second defect management reserved areas, the first defect management reserved area being used to store the defect management information in an initial state, and the second defect management reserved area being used to store the defect management information which is transited at a predetermined timing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromprior Japanese Patent Application No. 2003-78473, filed Mar. 20, 2003,the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an information recording medium whichcomprises a defect management area for storing defect managementinformation. The present invention also relates to an informationreproduction apparatus and information reproduction method forreproducing user data by acquiring defect management information from aninformation recording medium. The present invention further relates toan information recording method for recording defect information on aninformation recording medium.

2. Description of the Related Art

An information storage medium such as an optical disk has a user areaused to store user data, and has a mechanism for compensating fordefects generated in this user area. Such mechanism is called areplacement process. An area that manages information associated withthis replacement process, i.e., defect management information, is calleda DMA (Defect Management Area).

Of information recording media, a DVD-RAM allows 100,000 or moreoverwrite accesses. Even when the DMA of such medium with very highoverwrite durability undergoes tens of thousands of overwrite accesses,the reliability of the DMA does not drop.

For example, Jpn. Pat. Appln. KOKAI Publication No. 9-213011 discloses atechnique for improving the DMA reliability by allocating a plurality ofDMAs on an optical disk.

However, in the case of an information recording media having arelatively small allowable overwrite count (several ten to severalthousand times), overwrite accesses to a DMA of such a medium poses aproblem. That is, the DMA of such a medium is easily damaged byoverwrite accesses.

This problem cannot be solved even by the technique disclosed in Jpn.Pat. Appln. KOKAI Publication No. 9-213011. That is, even when aplurality of DMAs are allocated, since respective DMAs undergo overwriteaccesses at the same time, if one DMA is damaged by overwrite accesses,other DMAs are also damaged.

Each DMA stores defect management information, as described above, andif the DMA is damaged, defect management information cannot be read outfrom the DMA. As a result, the medium itself can no longer be used.Hence, it is demanded to improve the overwrite durability of the DMA.

BRIEF SUMMARY OF THE INVENTION

An information storage medium according to one aspect of the inventioncomprises a rewritable area, the rewritable area comprises a user areato store user data, and a defect management area to store defectmanagement information used to manage defective areas on the rewritablearea, the defect management area comprises first and second defectmanagement reserved areas, the first defect management reserved areabeing used to store the defect management information in an initialstate, and the second defect management reserved area being used tostore the defect management information which is transited at apredetermined timing.

An information reproduction apparatus according to one aspect of theinvention for reproducing information from an information storagemedium, which comprises a rewritable area, comprises an acquisition unitconfigured to acquire latest defect management information used tomanage defective areas on the rewritable areas from one of a pluralityof defect management reserved areas contained in a defect managementarea on the rewritable area, and a reproduction unit configured toreproduce user data from a user area on the rewritable area on the basisof the latest defect management information.

An information reproduction method according to one aspect of theinvention for reproducing information from an information storagemedium, which comprises a rewritable area, comprises acquiring latestdefect management information used to manage defective areas on therewritable areas from one of a plurality of defect management reservedareas contained in a defect management area on the rewritable area, andreproducing user data from a user area on the rewritable area on thebasis of the latest defect management information.

An information recording method according to one aspect of the inventionfor recording information on an information storage medium, whichcomprises a rewritable area, the rewritable area comprising a defectmanagement area to store defect management information used to managedefective areas on the rewritable area, and the defect management areacomprising first and second defect management reserved areas, the methodcomprises recording the defect management information on the firstdefect management reserved area in an initial state, and transiting thedefect management information to the second defect management reservedarea at a predetermined timing.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate presently preferred embodiments ofthe invention, and together with the general description given above andthe detailed description of the preferred embodiments given below, serveto explain the principles of the invention.

FIG. 1 shows an outline of the data structure of an information storagemedium (optical disk) according to an embodiment of the presentinvention;

FIG. 2 is a flow chart showing an example of a replacement process;

FIG. 3 shows an example of the data structure of a DMA allocated on theinformation storage medium;

FIG. 4 shows an example of contents described in a first sector of aDDS/PDL block contained in the DMA;

FIG. 5 shows an example of contents described in an SDL block containedin the DMA;

FIG. 6 shows an example of the data structure of one of a plurality ofSDL entries contained in an SDL;

FIG. 7 is a state transition chart for explaining an example of a methodof using a DMA sequence;

FIG. 8 shows the relationship (part 1) between the states of countersallocated in DMAs and DMA transition;

FIG. 9 shows the relationship (part 2) between the states of countersallocated in DMAs and DMA transition;

FIG. 10 is a flow chart showing an example of a sequence for searchingfor a currently active DMA;

FIG. 11 is a flow chart for explaining an example of DMA registrationand update processes;

FIG. 12 is a state transition chart for explaining an example of amethod of using a plurality of DMA sequences;

FIG. 13 is a view for explaining an example of lead-in and lead-outareas where a plurality of DMA sequences are allocated;

FIG. 14 is a flow chart showing an example of a reproduction process ofa medium on which a plurality of DMA sequences are allocated;

FIG. 15 is a schematic block diagram showing the arrangement of aninformation recording/reproduction apparatus according to an embodimentof the present invention;

FIG. 16 depicts an image of an example of DMA management by a DMAmanager;

FIG. 17 shows an example of the allocation of DMAs and manager storageareas on a medium, and the data structure in each manager storage area;

FIG. 18 shows an example of the data structure of a DMA manager storedin one manager reserved area in the manager storage area;

FIG. 19 shows an example of the allocation of DMA reserved areascontained in DMA sequence 1 to DMA sequence 4;

FIG. 20 shows an example of the relationship between the DMA and ECCblocks;

FIG. 21 shows an example of the allocation of DMA managers and DMAs;

FIG. 22 shows an example of DMA transition;

FIG. 23 shows an example of transition of DMA managers;

FIG. 24 shows an example of DMA conditions;

FIG. 25 shows an example of conditions of DMA reserved areas;

FIG. 26 is a view for explaining an example of an determination error ofa DMA reserved area in an abnormal state;

FIG. 27 shows an example of the allocation of DMAs and manager storageareas on a medium, and a sequence of DMA reserved areas contained ineach DMA;

FIG. 28 shows an example of the physical allocation of manager storageareas and DMAs on lead-in and lead-out areas;

FIG. 29 show areas which must be rewritten upon execution of areplacement process;

FIG. 30 shows an example of the contents of a PDL;

FIG. 31 shows an example of the contents of an SDL;

FIG. 32 is a flow chart showing an example of a DMA update process;

FIG. 33 is a flow chart showing an example of a DMA manager updateprocess;

FIG. 34 is a flow chart showing an example of a reproduction processbased on DMAs;

FIG. 35 shows an example of the data structure of an ECC block;

FIG. 36 shows an example of a scrambled frame allocation;

FIG. 37 shows an example of the data structure of an interleaved ECCblock; and

FIG. 38 shows an example of the data structure of recorded data fields.

DETAILED DESCRIPTION OF THE INVENTION

A preferred embodiment of the present invention will be describedhereinafter with reference to the accompanying drawings.

A first defect management method will be described hereinafter withreference to FIGS. 1 to 14. FIG. 1 shows an outline of the datastructure of an information storage medium (optical disk) according toan embodiment of the present invention. As shown in FIG. 1, aninformation storage medium has a data structure which comprises a sparearea SA and user area UA between DMAs. Note that the data structureshown in FIG. 1 is merely an example of that of the information storagemedium of the present invention, and the data structure of theinformation storage medium of the present invention is not limited tosuch a specific data structure.

The user area UA is used to store user data. The spare area SA is anarea where data to be recorded on a defective area present within theuser area is replacement-recorded. The defective area is an area forrespective ECC (Error Correction Code) blocks. That is, data forrespective ECC blocks is replacement-recorded on the spare area SA. Aswill be described later, each DMA may comprise a DMA counter (overwritemanagement area). The overwrite count on the DMA is reflected on thecount value of this DMA counter.

FIG. 2 is a flow chart showing a replacement process. As shown in FIG.2, data to be recorded on a defective area generated in the user area isreplacement-recorded on the spare area SA (ST1). In addition, the startaddresses of the replacement source (defective area) and replacementdestination (a predetermined area in the spare area SA) are registeredin an SDL (Secondary Defect List) in each DMA. The DMAs are allocated onthe inner and outer peripheries of the information recording medium, asshown in, e.g., FIG. 1, and identical data is registered in the SDLs ofboth the DMAs. When information is registered in each SDL, an updatecounter of the SDL is incremented (+1) (ST2)

Conventionally, a DMA is allocated at a fixed physical address on amedium. Furthermore, in order to improve the fault tolerance of the DMA,DMAs that store identical contents are allocated at a plurality oflocations on the medium. For example, in the case of a DVD-RAM, DMAs areallocated at two locations on the innermost periphery and two locationson the outermost periphery, i.e., a total of four locations, and thesefour DMAs record identical contents.

FIG. 3 is a schematic view showing the data structure of DMAs allocatedon the information storage medium of the present invention. As shown inFIG. 3, the information storage medium has a plurality of DMAs, each ofwhich is made up of DDS/PDL blocks and SDL blocks. “PDL” is anabbreviation for Primary Defect List. Each of the DDS/PDL and SDL blockscorresponds to one ECC block (=32 KB). A case will be exemplified belowwherein one ECC block consists of 32 KB, but one ECC block may consistof 64 KB. A 64 KB ECC block will be described in detail later.

In order to improve the fault tolerance of DMAs, when an active DMA hasweakened, the information storage medium of the present invention isdefined to shift defect management information stored in that DMA to anew DMA. It is determined that the DMA has weakened when the overwritecount of this DMA approaches an allowable overwrite count of the mediumhaving the DMA, or when defects on this DMA increase, and errorcorrection is more likely to fail.

Each DMA has a size of an integer multiple of that of an ECC block as atrue recording unit in a drive. On a DVD-RAM, one ECC block consists of16 sectors, and the size of one ECC block is 32 KB. A PDL is a primarydefect registration list, and an SDL is a secondary defect registrationlist. The PDL registers defect management information associated withdefects found in certification executed upon formatting a medium, i.e.,primary defects. By contrast, the SDL registers defect managementinformation associated with defects found upon normal recording (e.g.,upon recording user data), i.e., secondary defects. The defectmanagement information contains a replacement source address andreplacement destination address. When the sizes of these lists increase,the number of defects that can be registered increase. DMA0 to DMAn aresequentially allocated, and are used in turn from DMA0.

FIG. 4 shows an example of contents described in the first sector of theDDS/PDL block contained in the DMA. On a predetermined area of theDDS/PDL block, a 4-byte DDS/PDL update counter, 4-byte DMA rec-counter1, and the like are allocated.

Every time the contents of the DDS/PDL block are updated, the DDS/PDLupdate counter is incremented (+1). The DMA rec-counter 1 is counted upwhen the DDS/PDL block is rewritten. At the time of initialization(first time) of the medium, zero is set in all DMA rec-counters 1. Amethod of using this counter will be described later.

FIG. 5 shows an example of contents described in the SDL block containedin the DMA. On a predetermined area of the SDL block, a 4-byte SDLupdate counter, 4-byte DMA rec-counter 2, a plurality of SDL entries,and the like are allocated.

As in the DDS/PDL block, every time the contents of the SDL block areupdated, the SDL update counter is incremented (+1). The DMA rec-counter2 is counted up when the SDL block is rewritten. The SDL describesmanagement information associated with secondary defects. At the time ofinitialization (first time) of the medium, zero is set in all DMArec-counters 2. A method of using this counter will be described later.

FIG. 6 shows an example of the data structure of one of a plurality ofSDL entries contained in the SDL. One SDL entry consists of, e.g., 8bytes. On one SDL entry, a 3-byte field for describing the replacementsource address, and a 3-byte field for describing the replacementdestination address are allocated. A replacement process is done for,e.g., respective ECC blocks. The replacement source address field andreplacement destination address field respectively register theaddresses of first sectors contained in respective ECC blocks. In theexample of the data structure shown in FIG. 6, 3-byte fields areassigned to designate addresses. However, when a medium has a largercapacity (larger address space), the address designation field sizeincreases.

FIG. 7 is a state transition chart for explaining the method of using aDMA sequence. The DMA sequence comprises (n+1) DMAs from DMA0 to DMAn.If DMA0 is a currently active DMA, DMA1 to DMAn are auxiliary DMAs.

A plurality of DMAs included in the DMA sequence are used in turn fromDMA0. In an initial state (ST1-1), DMA0 is used, and DMA1 and subsequentDMAs are not used. When defects on DMA0 increase, or when the overwritecount has exceeded a prescribed value, DMA0 becomes a used area, anddefect management information stored in DMA0 is replaced to and recordedon DMA1 (ST2-1). Likewise, using DMAs in turn, even when each DMA hassuffered defects or overwrite damage, the medium can be continuouslyused without breaking down as a system.

FIG. 8 shows the relationship (part 1) between the states of countersallocated in DMAs and DMA transition. The DDS/PDL update counter and SDLupdate counter shown in FIG. 8 are cumulative counters whichcumulatively count even when DMA transition has occurred (even aftertransition of DMA0→DMA1).

As shown in FIG. 8, a DMA counter is allocated on a predetermined areaof a DMA. This DMA counter is incremented when the DMA is rewritten.That is, a larger one of the count value of the DMA rec-counter 1 of theDDS/PDL block contained in the DMA and that of the DMA rec-counter 2 ofthe SDL block contained in the DMA is the count value of the DMAcounter.

More specifically, by checking the count value of this DMA counter, theoverwrite count of the currently active DMA can be detected. In otherwords, the count value of the DMA counter is a value indicating thelevel of damage that the DMA suffers upon overwrite accesses on the DMA.

An information recording/reproduction apparatus for recordinginformation on this medium shifts the currently active DMA (e.g., DMA0)to an auxiliary DMA (e.g., DMA1) within the range of the allowableoverwrite count (Nov) which is determined in accordance with thecharacteristics of a medium. Of course, in order to fully effectivelyuse the currently active DMA, it is desirable to use that DMA until themaximum value (Nov-1) of the DMA counter. Even when the DMA counter doesnot reach its maximum value, the information recording/reproductionapparatus shifts the currently active DMA to an auxiliary DMA if itdetects an increase of defects on the currently active DMA. Each DMAreceives a value only after start of use. That is, no value is input tounused DMAs. When a medium is loaded to the informationrecording/reproduction apparatus, the information recording/reproductionapparatus searches for a DMA in which the count values of both DMArec-counters 1 and 2 are zero, so as to detect the location of thecurrently active DMA. If a DMA (e.g., DMA2) in which the count values ofboth DMA rec-counters 1 and 2 are zero is found, the apparatusrecognizes a DMA (e.g., DMA1) immediately before the found DMA as thecurrently active DMA. If no DMA in which the count values of both DMArec-counters 1 and 2 are zero is found, the apparatus recognizes thelast DMA (e.g., DMAn) as the currently active DMA.

FIG. 9 shows the relationship (part 2) between the states of countersallocated in DMAs and DMA transition. The case has been explained abovewith reference to FIG. 8 wherein the DDS/PDL update counter and SDLupdate counter cumulatively count even when DMA transition has occurred.By contrast, FIG. 9 will explain a case wherein the count values of theDDS/PDL update counter and SDL update counter are reset when DMAtransition has occurred (after transition of DMA0→DMA1).

As shown in FIG. 9, a DMA counter is allocated on a predetermined areaof a DMA. This DMA counter is incremented when the DMA is rewritten.That is, a larger one of the count value of the DDS/PDL update counter(DMA rec-counter 1) of the DDS/PDL block contained in the DMA and thatof the SDL update counter (DMA rec-counter 2) of the SDL block containedin the DMA is the count value of the DMA counter.

In the case shown in FIG. 9, every time the DMA shifts, the DDS/PDLupdate counter and SDL update counter are reset. For this reason, theDDS/PDL update counter has a function equivalent to that of the DMArec-counter 1, and the SDL update counter has a function equivalent tothat of the DMA rec-counter 2. Therefore, in the case shown in FIG. 9,DMA rec-counters 1 and 2 may be omitted.

FIG. 10 is a flow chart showing the sequence for searching for thecurrently active DMA. The search process for searching for the currentlyactive DMA is executed by a main controller 20 of the informationrecording/reproduction apparatus shown in FIG. 15. As described above,the information storage medium of the present invention is defined toshift DMAs upon overwrite accesses and the like. Therefore, when a diskis loaded to the information recording/reproduction apparatus, thecurrently active DMA must be searched for. The DMA rec-counters 1 and 2are allocated on each of DMAs (DMA0 to DMAn) on the medium. When themedium is initialized, the count values of the DMA rec-counters 1 and 2of each DMA are set to zero. When use of the medium begins, the countvalues of the DMA rec-counters 1 and 2 of DMA1 are counted up. When useof the medium further continues, the count values of the DMArec-counters 1 and 2 of DMA2 are counted up. The use order of DMA0 toDMAn is predetermined. That is, the DMAs are used in the order ofDMA0→DMA1→DMA2→. . . →DMAn. Hence, by checking the count values of theDMA rec-counters 1 and 2 of DMA0 to DMAn, the currently active DMA canbe found out.

As shown in FIG. 10, when the medium is loaded to the informationrecording/reproduction apparatus, the information recording/reproductionapparatus searches for a DMA in which the count values of both DMArec-counters 1 and 2 are zero, so as to detect the location of thecurrently active DMA (ST21). If a DMA (e.g., DMA2) in which the countvalues of both DMA rec-counters 1 and 2 are zero is found (ST22, YES),the apparatus recognizes a DMA (e.g., DMA1) immediately before the foundDMA as the currently active DMA (ST24). If no DMA in which the countvalues of both DMA rec-counters 1 and 2 are zero is found (ST22, NO),the apparatus recognizes the last DMA (e.g., DMAn) as the currentlyactive DMA (ST23).

FIG. 11 is a flow chart for explaining DMA registration and updateprocesses. The DMA registration and update processes are executed by themain controller 20 of the information recording/reproduction apparatusshown in FIG. 15. The main controller 20 checks based on the count valueof the DMA counter of the DMA if the rewrite count of the currentlyactive DMA has exceeded a prescribed value (ST31). If it is determinedthat the rewrite count has exceeded the prescribed value (ST31, YES),the main controller 20 confirms if defect information stored in thecurrently active DMA can be shifted (if an auxiliary DMA remains). If itis determined that defect information can be shifted (ST34, YES), themain controller 20 shifts defect information stored in the currentlyactive DMA to a DMA determined as the next shift destination (ST35). Atthis time, required values are taken over. For example, in the caseshown in FIG. 8, the values of the DDS/PDL update counter and SDL updatecounter are taken over.

Even if the rewrite count is equal to or smaller than the prescribedvalue (ST31, NO), if the main controller 20 detects that many defectsare generated in the DMA (ST32, YES), the controller 20 confirms ifdefect information stored in the currently active DMA can be shifted (ifan auxiliary DMA remains). If it is determined that defect informationcan be shifted (ST34, YES), the main controller 20 shifts defectinformation stored in the currently active DMA to a DMA determined asthe next shift destination (ST35). If it is determined that defectinformation cannot be shifted (ST34, NO), this process terminatesabnormally.

If the rewrite count of the currently active DMA is equal to or smallerthan the prescribed value (ST31, NO) and if the currently active DMAdoes not suffer defects (ST32, NO), the currently active DMA is updatedas needed (ST33).

FIG. 12 is a state transition chart for explaining an example of amethod of using a plurality of DMA sequences. As shown in FIG. 7, use ofa single DMA sequence has been explained so far. That is, the case hasbeen explained wherein one DMA sequence includes DMA0 to DMAn. In thiscase, use of a plurality of DMA sequences, as shown in FIG. 12, will beexplained. That is, a case will be explained wherein each of a pluralityof DMA sequences includes DMA0 to DMAn.

As shown in FIG. 12, for example, an information storage medium havingfour DMA sequences will be explained. The four DMA sequences areallocated at different locations. For example, DMA sequences 1 and 2 areallocated on the innermost periphery of the medium, and DMA sequences 3and 4 are allocated on the outermost periphery of the medium. Assumethat it is detected that many defects are generated in, e.g., DMAsequence 3 of DMA sequences 1 to 4 (initial state of FIG. 12). The maincontroller of the information recording/reproduction apparatus shown inFIG. 15 detects the presence of many defects. Upon detection of defects,defect management information in each of currently active DMAs (e.g.,DMA0) in all the DMA sequences is shifted (undergoes replacementrecording) to the next DMA (e.g., DMA1) (second state in FIG. 12). Themain controller of the information recording/reproduction apparatusshown in FIG. 15 shifts (executes replacement recording of) the defectmanagement information.

FIG. 13 is a view for explaining lead-in and lead-out areas where aplurality of DMA sequences are allocated. As shown in FIG. 13, a medium(optical disk) 1 has a lead-in area A1 on its innermost periphery, and alead-out area A3 on its outermost periphery. Also, the medium 1 has adata area A2 between the lead-in and lead-out areas A1 and A3. The dataarea A2 has a user area UA and spare area SA.

The lead-in area A1 on the innermost periphery comprises first DMAsequences (DMA sequences 1 and 2), and the lead-out area A3 on theoutermost periphery comprises second DMA sequences (DMA sequences 3 and4). In this way, by allocating the DMA sequences on the innermost andoutermost peripheries, a plurality of DMA sequences are allocated atphysically separated locations. As a result, DMAs become invulnerable tofailures.

FIG. 14 is a flow chart of a reproduction process of a medium on which aplurality of DMA sequences are allocated. When a medium is loaded to theinformation recording/reproduction apparatus shown in FIG. 15, theapparatus searches all DMA sequences for currently active DMAs, andreads out defect management information from the currently active DMAs(ST41). That is, in the case of, e.g., FIG. 12, the apparatus searchesDMA sequence 1 for a currently active DMA (e.g., DMA1), DMA sequence 2for a currently active DMA (e.g., DMA1), DMA sequence 3 for a currentlyactive DMA (e.g., DMA1), and DMA sequence 4 for a currently active DMA(e.g., DMA1). The process for searching for the currently active DMA isas shown in FIG. 10.

If no defect management information can be read out from any of DMAs dueto the influence of failures or the like (ST42, NO), this processterminates abnormally. If defect management information can be read outfrom the DMAs, the apparatus checks the count values of the DDS/PDLupdate counter and SDL update counter of each DMA. The currently activeDMAs in the plurality of DMA sequences should record identicalinformation. Therefore, the count values of the DDS/PDL update countersand SDL update counters of the respective DMAs should match. However, ifany failure has occurred during a process of recording information onthe respective DMAs in the plurality of DMA sequences in turn, some DMAsmay remain unupdated. If the currently active DMAs in the plurality ofDMA sequences have different count values of the update counters (ST43,NO), the unupdated DMAs match the DMAs having the latest count values(ST44). In this way, preparation for recording/reproduction iscompleted.

FIG. 15 shows a schematic arrangement of the informationrecording/reproduction apparatus according to an embodiment of thepresent invention. This information recording/reproduction apparatusrecords user data on the aforementioned medium (optical disk) 1, andreproduces user data recorded on the medium 1. Also, this informationrecording/reproduction apparatus executes a replacement process asneeded.

As shown in FIG. 15, the information recording/reproduction apparatuscomprises a modulation circuit 2, laser control circuit 3, laser 4,collimator lens 5, polarization beam splitter (to be referred to as aPBS hereinafter) 6, quarter wave plate 7, objective lens 8, focusinglens 9, photodetector 10, signal processing circuit 11, demodulationcircuit 12, focus error signal generation circuit 13, tracking errorsignal generation circuit 14, focus control circuit 16, tracking controlcircuit 17, and main controller 20.

The main controller 20 controls a drive unit. The drive unit includesthe modulation circuit 2, laser control circuit 3, laser 4, collimatorlens 5, PBS 6, quarter wave plate 7, objective lens 8, focusing lens 9,photodetector 10, signal processing circuit 11, demodulation circuit 12,focus error signal generation circuit 13, tracking error signalgeneration circuit 14, focus control circuit 16, and tracking controlcircuit 17.

A data recording process of this information recording/reproductionapparatus will be described below. The data recording process iscontrolled by the main controller 20. Recording data (data symbol) ismodulated to a predetermined channel bit sequence by the modulationcircuit 2. The channel bit sequence corresponding to the recording datais converted into a laser drive waveform by the laser control circuit 3.The laser control circuit 3 pulse-drives the laser 4 to record datacorresponding to a desired bit sequence on the medium 1. A recordinglaser beam emitted by the laser 4 is converted into collimated light bythe collimator lens 5. The collimated light enters and is transmittedthrough the PBS 6. The beam transmitted through the PBS 6 passes throughthe quarter wave plate 7, and is focused on the information recordingsurface of the medium 1 by the objective lens 8. The focused beam ismaintained in a state wherein it can form a best small spot on therecording surface, under the focus control of the focus control circuit16 and the tracking control of the tracking control circuit 17.

A data reproduction process of this information recording/reproductionapparatus will be described below. The data reproduction process iscontrolled by the main controller 20. The laser 4 emits a reproductionlaser beam on the basis of a data reproduction instruction from the maincontroller 20. The reproduction laser beam emitted by the laser 4 isconverted into collimated light by the collimator lens 5. The collimatedlight enters and is transmitted through the PBS 6. The beam transmittedthrough the PBS 6 passes through the quarter wave plate 7, and isfocused on the information recording surface of the medium 1 by theobjective lens 8. The focused beam is maintained in a state wherein itcan form a best small spot on the recording surface, under the focuscontrol of the focus control circuit 16 and the tracking control of thetracking control circuit 17. At this time, the reproduction laser beamthat strikes the medium 1 is reflected by a reflection film orreflective recording film in the information recording surface. Thereflected light is transmitted through the objective lens 8 in thereverse direction, and is converted into collimated light again. Thereflected light is transmitted through the quarter wave plate 7, and isreflected by the PBS 6 since it has a plane of polarizationperpendicular to the incoming light. The beam reflected by the PBS 6 isconverted into convergent light by the focusing lens 9, and enters thephotodetector 10. The photodetector 10 comprises, e.g., a 4-splitphotodetector. The light beam that has entered the photodetector 10 isphotoelectrically converted into an electrical signal, which is thenamplified. The amplified signal is equalized and binarized by the signalprocessing circuit 11, and is then supplied to the demodulation circuit12. The signal undergoes demodulation corresponding to a predeterminedmodulation method in the demodulation circuit 12, thus outputtingreproduction data.

The focus error signal generation circuit 13 generates a focus errorsignal on the basis of some components of the electrical signal outputfrom the photodetector 10. Likewise, the tracking error signalgeneration circuit 14 generates a tracking error signal on the basis ofsome components of the electrical signal output from the photodetector10. The focus control circuit 16 controls focusing of a beam spot on thebasis of the focus error signal. The tracking control circuit 17controls tracking of a beam spot on the basis of the tracking errorsignal.

The replacement process of the main controller 20 will be describedbelow. Upon formatting a medium, certification is executed. At thistime, the main controller 20 detects defects on the medium. The maincontroller 20 records defect management information associated withdefects detected at that time, i.e., primary defects, on the PDL in theDMA of that medium. The defect management information contains areplacement source sector address, and replacement destination sectoraddress. In normal recording, the main controller 20 also detectsdefects on the medium. The main controller 20 records defect managementinformation associated with defects detected at that time, i.e.,secondary defects, on the SDL in the DMA of that medium. The defectmanagement information contains the addresses of the first sectors ofECC blocks as the replacement source and destination. Based on the PDLand SDL, an access to the replacement source is considered as that tothe replacement destination. The main controller 20 controls the searchprocess of the currently active DMA shown in FIG. 10, the DMAregistration and update processes shown in FIG. 11, the reproductionprocess shown in FIG. 14, and the like.

A second defect management method will be described hereinafter withreference to FIGS. 16 to 38. The second defect management method isdefect management which follows that shown in FIG. 12, and furtherexploits a DMA manager. In the description of the second defectmanagement method, contents that overlap those of the first defectmanagement method shown in FIGS. 1 to 15 will refer to the alreadyexplained drawings, as needed.

An information storage medium of the present invention comprises arewritable area, which comprises a plurality of DMA sequences, aplurality of manager storage areas, and a user area. On the medium shownin FIG. 13, the rewritable area is included in the lead-in area A1, dataarea A2, and lead-out area A3. The plurality of DMA sequences storeidentical defect management information. As a result, the faulttolerance of the DMAs can be improved.

As shown in FIGS. 16 and 17, for example, an information storage mediumcomprises DMA sequence 1, DMA sequence 2, DMA sequence 3, and DMAsequence 4. More specifically, DMA sequence 1 and DMA sequence 2 areallocated on the lead-in area Al (lead-in area LI shown in FIG. 17) onthe innermost periphery of the information storage medium shown in FIG.13, and DMA sequence 3 and DMA sequence 4 are allocated on the lead-outarea A3 (lead-out area LO shown in FIG. 17) on the outermost peripheryof the information storage medium. The respective DMA sequences (DMAsequence 1, DMA sequence 2, DMA sequence 3, and DMA sequence 4) comprisea plurality of DMA reserved areas (DMA sets #1-1 to #1-N, DMA sets #2-1to #2-N, DMA sets #3-1 to #3-N, and DMA sets #4-1 to #4-N). In aninitial state, the first DMA reserved areas (DMA set #1-1, DMA set #2-1,DMA set #3-1, and DMA set #4-1) contained in the respective DMAsequences store current (latest) defect management information. If thefirst DMA reserved area (e.g., DMA set #1-1) contained in an arbitraryDMA sequence (e.g., DMA sequence 1) falls under a defective area, allpieces of defect management information stored in the first DMA reservedareas (DMA set #1-1, DMA set #2-1, DMA set #3-1, and DMA set #4-1) ofall the DMA sequences (DMA sequence 1 to DMA sequence 4) are transitedto the second DMA reserved areas (DMA set #1-2, DMA set #2-2, DMA set#3-2, and DMA set #4-2) of all the DMA sequences.

As described above, on the information storage medium of the presentinvention, currently active DMA reserved areas transit. Based on this, aDMA manager used to quickly search a plurality of DMA reserved areas forcurrently active DMA reserved areas is introduced. That is, theinformation storage medium of the present invention comprises managerstorage areas for storing DMA managers, as shown in FIG. 17. Each DMAmanager manages the addresses of the currently active DMA reservedareas. In other words, each manager storage area is a locationinformation area for storing the location information of the currentlyactive DMA reserved areas.

FIG. 16 shows address management of the currently active DMA reservedareas by the DMA manager. DMA sequence 1 comprises N DMA reserved areas(DMA set #1-1 to DMA set #1-N). Likewise, DMA sequence 2 comprises N DMAreserved areas (DMA set #2-1 to DMA set #2-N). Likewise, DMA sequence 3comprises N DMA reserved areas (DMA set #3-1 to DMA set #3-N). Likewise,DMA sequence 4 comprises N DMA reserved areas (DMA set #4-1 to DMA set#4-N).

For example, assume that the first DMA reserved areas (DMA set #1-1, DMAset #2-1, DMA set #3-1, and DMA set #4-1) are currently active. In thiscase, the DMA manager has location information (addresses) indicatingthe positions (e.g., head positions) of the first DMA reserved areas(DMA set #1-1, DMA set #2-1, DMA set #3-1, and DMA set #4-1).

As shown in FIG. 17, for example, the manager storage areas (Man1, Man2)are respectively allocated on the lead-in and lead-out areas. Themanager storage area (Man1) allocated on the lead-in area, and that(Man2) allocated on the lead-out area store identical information.

Furthermore, each of the manager storage areas (Man1, Man2) comprises aplurality of manager reserved areas. This is to take a measure againstdefects of the DMA manager. As shown in FIG. 17, one manager storagearea (Man1) comprises 10 manager reserved areas (DMA_Man#1 toDMA_Man#10). Likewise, the other manager storage area (Man2) comprises10 manager reserved areas (DMA_Man#1 to DMA_Man#10).

For example, in the initial stage, the first manager reserved areas(DMA_Man#1) contained in the respective manager storage areas (Man1,Man2) store the location information indicating the currently active DMAreserved areas. As a result of overwrite accesses, when the firstmanager reserved area (DMA_Man#1) contained in a given manager storagearea (Man1) falls under a defective area, all pieces of locationinformation stored in the first manager served areas (DMA_Man#1) of allthe manager storage areas (Man1, Man2) are transited (transferred) tothe second manager reserved areas (DMA_Man#2) of all the manager storageareas (Man1, Man2).

Note that the DMA manager has a lower rewrite frequency than DMAs. Forthis reason, the manager storage areas (Man1, Man2) that store the DMAmanagers, i.e., the manger reserved areas are unlikely to becomedefective areas as a result of overwrite accesses compared to the DMAs.However, the DMA manager cannot often be read out from the managerreserved area due to scratches, fingerprints, and the like. Hence, oneDMA manager has a plurality of identical contents (the locationinformation of the currently active DMAs). That is, identical contentsare written in each manager reserved area a plurality of number oftimes. In this way, even when error correction as an ECC block hasfailed, data (location information of the currently active DMAs) can beread out.

One DMA manager is stored in one manager reserved area. The managerreserved area consists of one ECC block. In one ECC block that forms themanager reserved area, identical contents each of 64 bytes are written aplurality of times. Assume that one ECC block consists of 32 sectors.Also, assume that one sector consists of 2048 bytes. That is, assumethat the size of one ECC block is 2048 bytes×32 sectors. In this case,32 identical contents are recorded in each sector. That is, 32×32identical contents are repetitively recorded in one ECC block. Even whenthere are too many defects to correct a full ECC block, correctinformation (location information of the currently active DMAs) is morelikely to be read out as long as an ECC block can be partiallycorrected. ECC blocks will be described in detail later with referenceto FIGS. 35 to 38.

The multiple write process in 64 bytes has been explained, but thepresent invention is not limited to such specific process. As shown inFIGS. 35 and 36, one data line in one ECC block is 172 bytes. Even whena full ECC block cannot undergo error correction, error correction maybe made for respective 172-byte data lines. Focusing attention on thispoint, when identical information is written a plurality of number oftimes in a data size (e.g., 64 bytes) sufficiently smaller than 172bytes, correct data can be obtained by error correction for respectivedata lines even when a full ECC block cannot undergo error correction.

FIG. 18 shows an example of the DMA manager. As shown in FIG. 18, theDMA manager manages the addresses of the currently active, four DMAreserved areas. For example, the DMA manager manages the addresses ofDMA set #1-1, DMA set #2-1, DMA set #3-1, and DMA set #4-1. Area numbersmay be described in place of the addresses as long as the locations ofthe currently active DMA reserved areas can be uniquely specified.

FIG. 19 shows the configuration of the four DMA sequences (DMA sequence1 to DMA sequence 4). FIG. 20 shows the relationship between the DMA andECC blocks. As shown in FIG. 19, one DMA reserved area contains aDDS/PDL block SDL block, and RSV (reserved) block. The purpose of theRSV block is to avoid continued occurrence of defects by assuring agiven physical distance between successive DMA reserved areas. That is,each DMA reserved area stores the DDS/PDL block and SDL block inpractice, as shown in FIG. 20.

FIG. 30 shows the contents of the PDL. A maximum of 15871 PDL entriesare allowed ((2048×31−4)/4=15871). FIG. 31 shows the contents of theSDL. A maximum of 8189 SDL entries are allowed ((2048×31−24)/8=8189).

Each of the DMA sequences (DMA sequence 1, DMA sequence 2, DMA sequence3, and DMA sequence 4) comprises, e.g., 100 DMA reserved areas. That is,a total of 400 DMA reserved areas are assured. One DMA reserved areaconsists of three blocks, as described above. Therefore, a total of 1200blocks are assured.

As described above, DMA sequence 1 and DMA sequence 2 are allocated onthe lead-in area. The k-th DMA reserved areas contained in DMA sequence1 and DMA sequence 2 record identical defect management information.That is, the k-th DMA reserved areas contained in DMA sequence 1 and DMAsequence 2 are used at the same time. More specifically, the k-th DMAreserved areas contained in DMA sequence 1 and DMA sequence 2 can beefficiently accessed when they are physically close to each other.Hence, the physical allocation in which the k-th DMA reserved areascontained in DMA sequence 1 and DMA sequence 2 are allocated to be closeto each other is adopted.

For example, as shown in FIGS. 19 and 27, the DMA reserved areas in DMAsequence 1 and DMA sequence 2 are allocated in the order of the firstDMA reserved area (DMA set #1-1) contained in DMA sequence 1→the firstDMA reserved area (DMA set #2-1) contained in DMA sequence 2→the secondDMA reserved area (DMA set #1-2) contained in DMA sequence 1→the secondDMA reserved area (DMA set #2-2) contained in DMA sequence 2→. . . →theN-th DMA reserved area (DMA set #1-N) contained in DMA sequence 1→theN-th DMA reserved area (DMA set #2-N) contained in DMA sequence 2. Withthis allocation, the read-out time of defect management information fromthe currently active DMA reserved areas contained in DMA sequence 1 andDMA sequence 2 can be shortened. Furthermore, the time required for atransition process (transfer process) of defect management informationfor the DMA reserved areas contained in DMA sequence 1 and DMA sequence2 can also be shortened.

The same applies to DMA sequence 3 and DMA sequence 4 allocated on thelead-out area. That is, as shown in FIG. 19, the DMA reserved areas inDMA sequence 3 and DMA sequence 4 are allocated in the order of thefirst DMA reserved area (DMA set #3-1) contained in DMA sequence 3→thefirst DMA reserved area (DMA set #4-1) contained in DMA sequence 4→thesecond DMA reserved area (DMA set #3-2) contained in DMA sequence 3→thesecond DMA reserved area (DMA set #4-2) contained in DMA sequence 4→. .. →the N-th DMA reserved area (DMA set #3-N) contained in DMA sequence3→the N-th DMA reserved area (DMA set #4-N) contained in DMA sequence 4.

However, when the access speed is not that important, the respective DMAreserved areas may be allocated to be physically distant from eachother. With this allocation, DMAs immune to causes of defects such asscratches, fingerprints, and the like can be formed. The physicalallocation of DMA sequence 1 to DMA sequence 4 can be determined basedon desired balance between the required access speed and reliability.

FIGS. 21 and 28 show the allocation of the DMA managers and DMAs. TheDMA managers are stored in the manager reserved areas (DMA Manager 1-1to DMA Manager 1-10) on the lead-in area, and those (DMA Manager 2-1 toDMA Manager 2-10) on the lead-out area. Two DMA sequences (DMA sequence1, DMA sequence 2) are allocated on the lead-in area, and two DMAsequences (DMA sequence 3, DMA sequence 4) are allocated on the lead-outarea.

FIG. 22 shows transition of the DMA sequences. As shown in FIG. 22, fourDMA sequences transit at the same time. Compared to a case wherein eachDMA sequence independently transits, the physical distance among DMAsequences can be prevented from being increased by transiting the fourDMA sequences at the same time. As a result, access performance can beprevented from deteriorating. Also, easy recovery is allowed uponoccurrence of any system failures.

In the initial state (ST2-1), the head (first) DMA reserved areas (DMAset #1-1, DMA set #2-1, DMA set #3-1, and DMA set #4-1) of therespective DMA sequences (DMA sequence 1, DMA sequence 2, DMA sequence3, and DMA sequence 4) are activated. If one or more of the head DMAreserved areas (DMA set #1-1, DMA set #2-1, DMA set #3-1, and DMA set#4-1) of the respective DMA sequences fall under defective areas,transition of defect management information is made to the second DMAreserved areas (DMA set #1-2, DMA set #2-2, DMA set #3-2, and DMA set#4-2) of the respective DMA sequences (ST2-2). Likewise, transition ofdefect management information is made in turn. When the defectmanagement information reaches the N-th DMA reserved areas (DMA set#1-N, DMA set #2-N, DMA set #3-N, and DMA set #4-N) of the respectiveDMA sequences, the recording operation is inhibited (ST2-N). After that,the medium is handled as a read-only medium.

FIG. 23 shows transition of the DMA managers. The DMA managers also maketransition as in the DMAs. That is, in the initial state, the latest DMAmanagers are stored in the head (first) manager reserved areas(DMA_Man#1-1, DMA_Man#2-1) of the respective manager storage areas(Man1, Man2). When one or more of the head manager reserved areas(DMA_Man#1-1, DMA-Man#2-1) in the manager storage areas fall underdefective areas, the DMA managers are transited to the second managerreserved areas (DMA_Man#1-2, DMA_Man#2-2) in the manager storage areas.Likewise, transition of the DMA managers is made in turn. When the DMAmanagers reach the N-th manager reserved areas (DMA_Man#1-N,DMA_Man#2-N) in the manager storage areas, the recording operation isinhibited.

FIG. 24 shows DMA conditions. Normally, a DMA reserved area which isdetermined to fall under a defective area once should successively fallunder a defective area. However, a DMA reserved area which is determinedby accident (e.g., attachment of dust or the like) to fall under adefective area may be determined later not to fall under a defectivearea. That is, data may be correctly read out later from even a DMAreserved area which is determined to fall under a defective area once.

Normally, when the first DMA reserved area falls under a defective area,information must be transited. However, when the first DMA reserved areafalls under a defective area due to some cause, defect managementinformation may be transited to the third or fourth DMA reserved area.In such case, the second DMA reserved area is set in a reserved state.That is, the second DMA reserved area is determined as a blank area. Ina normal state, defect management information can be correctly read outfrom the currently active DMA reserved area. However, in an abnormalstate, the currently active DMA reserved area may fall under a defectivearea or may be a blank area. A determination error of a defective areaoften results in unwanted transition of the DMA reserved area. That is,the state of the DMA reserved area cannot be simply determined based ononly the read-out state.

FIG. 25 shows the normal state of the DMA reserved areas. As shown inFIG. 25, for example, cases 1 to 5 are possible. As described above, theDMA sequences comprise a plurality of DMA reserved areas. The head DMAreserved areas (DMA set #1-1, DMA set #2-1, DMA set #3-1, and DMA set#4-1) of the plurality of DMA reserved areas are represented by “head”,the last DMA reserved areas (DMA set #1-N, DMA set #2-N, DMA set #3-N,and DMA set #4-N) are represented by “tail”, and some DMA reserved areasbetween the head and last DMA reserved areas are represented by “body”.

Case 1 indicates an unformatted information storage medium. That is, allDMA reserved areas corresponding to “head”, “body”, and “tail” are in areserved state.

Case 2 indicates an initialized information storage medium. That is, theDMA reserved areas corresponding to “head” are currently active, andthose which correspond to “body” and “tail” are in a reserved state.

Case 3 indicates an information storage medium after DMA transition.That is, the DMA reserved areas corresponding to “head” are defectiveareas, predetermined DMA reserved areas of some DMA reserved areascorresponding to “body” are currently active areas, and DMA reservedareas after these currently active DMA reserved areas are in a reservedstate.

Case 4 indicates an information storage medium in a final stage. Thatis, the DMA reserved areas corresponding to “head” and “body” aredefective areas, and those which correspond to “tail” are currentlyactive areas.

Case 5 indicates an unusable information storage medium. That is, allDMA reserved areas corresponding to “head”, “body”, and “tail” aredefective areas.

Note that an identifier indicating a reserved state may be stored in anarea in a reserved state so as to easily identify the reserved state.

The information recording/reproduction apparatus (main controller 20) ofthe present invention shown in FIG. 15 supports both a Table lookupscheme and Incremental scheme as a scheme for searching for thecurrently active DMAs. That is, the information storage medium of thepresent invention adopts a hybrid search format (HSF) that can applyboth the Table lookup scheme and Incremental scheme. Normally, the maincontroller 20 searches for the currently active DMAs by the Table lookupscheme. The Table lookup scheme searches for the currently active DMAsbased on the DMA managers. If the DMA managers cannot be read out, themain controller 20 searches for the currently active DMAs by theIncremental scheme. The Incremental scheme checks all DMA reserved areascontained in the DMAs in turn to search for the currently active DMAs.That is, the Incremental scheme is if the Table lookup scheme fails.

As has been explained using FIG. 24, if the currently active DMAreserved areas are searched for using only the Incremental scheme, adetermination error of the currently active DMA reserved areas mayoccur. FIG. 26 shows an example of a determination error of the DMAreserved areas in an abnormal state. For example, defect managementinformation stored in the first (head) DMA reserved areas may betransited to the (2+α)-th DMA reserved areas after the second DMAreserved areas in some cases. Normally, defect management informationstored in the first (head) DMA reserved areas must be transited to thesecond DMA reserved areas. However, when the second DMA reserved areascannot be activated due to failures such as address errors or the likeof the second DMA reserved areas, the (2+α)-th DMA reserved areas afterthe second DMA reserved areas are activated. However, if defectmanagement information can be read out from, e.g., the first (head) DMAreserved areas after this transition, it is erroneously determined thatthe first (head) DMA reserved areas are currently active. In order toprevent such determination error, upon making a search by theIncremental scheme, a sufficiently large window width must be used indetermination, resulting in a long determination time. Hence, theinformation recording/reproduction apparatus of the present inventionpreferentially uses the Table lookup scheme that allows high-speedsearch, and searches using the Incremental method only when the Tablelookup scheme cannot find any currently active DMA reserved areas.

FIG. 29 shows areas which must be rewritten upon a replacement process.For example, when it is determined that a predetermined area on the userarea falls under a defective area, information to be recorded on thispredetermined area is replacement-recorded on a spare area. As a result,the address of this predetermined area (replacement source) and that ofthe spare area (replacement destination) are recorded in the k-th DMAreserved areas of the respective DMA sequences (DMA sequence 1 to DMAsequence 4) as defect management information. The DMA managers arerewritten when DMA transition occurs. Therefore, the rewrite frequencyof the DMA managers is low.

FIG. 32 is a flow chart showing an overview of the DMA update process.As shown in FIG. 32, the main controller 20 of the informationrecording/reproduction apparatus shown in FIG. 15 searches for thecurrently active DMA reserved areas by the Table lookup scheme (ST101).That is, if location information indicating the currently active DMAreserved areas can be read out from the latest DMA managers, thecurrently active DMA reserved areas can be found out (ST102, YES). Ifthe main controller 20 cannot find any currently active DMA reservedareas by the Table lookup scheme (ST102, NO), it searches for thecurrently active DMA reserved areas by the Incremental scheme (ST103).If the main controller 20 cannot find any currently active DMA reservedareas by the Incremental scheme (ST104, NO), the DMA update processfails (ST105).

If the currently active DMA reserved areas are found (ST102, YES)(ST104, YES), the main controller 20 determines whether or nottransition of the currently active DMA reserved areas is required(ST106). If at least one of the currently active DMA reserved areasfalls under a defective area, the main controller 20 determines thattransition of the currently active DMA reserved areas is required(ST106, YES).

If no transition is required (ST106, NO), the main controller 20 updatesthe defect management information stored in the currently active DMAreserved areas in correspondence with the replacement process (ST108).If transition is required (ST106, YES), the main controller 20 transfersdefect management information stored in the currently active DMAreserved areas to new DMA reserved areas (next DMA reserved areas)(ST107), and updates the defect management information in correspondencewith the replacement process (ST108).

FIG. 33 is a flow chart showing an overview of the DMA manager updateprocess. The main controller 20 determines first whether or nottransition of the current DMA managers is required (ST111). If at leastone of the manager reserved areas that store the currently active DMAmanagers falls under a defective area, the main controller 20 determinesthat transition of the currently active DMA managers is required (ST111,YES). If transition is required (ST111, YES), the main controller 20transfers the currently active DMA managers to new manager reservedareas (next manager reserved areas) (ST112). Also, if DMA transition hasoccurred (ST113, YES), the main controller 20 updates the DMA managersupon transition of the DMA (ST114).

FIG. 34 is a flow chart showing an overview of the reproduction processbased on the DMAs. As shown in FIG. 34, the main controller 20 of theinformation recording/reproduction apparatus shown in FIG. 15 searchesfor the currently active DMA reserved areas by the Table lookup scheme(ST121). That is, if location information indicating the currentlyactive DMA reserved areas can be read out from the latest DMA managers,the currently active DMA reserved areas can be found out (ST122, YES).If the main controller 20 of the information recording/reproductionapparatus cannot find any currently active DMA reserved areas by theTable lookup scheme (ST122, NO), it searches for the currently activeDMA reserved areas by the Incremental scheme (ST123). If the maincontroller 20 cannot find any currently active DMA reserved areas by theIncremental scheme (ST124, NO), the reproduction process fails (ST125).

If the currently active DMA reserved areas are found (ST122, YES)(ST124, YES), defect management information is read out from thecurrently active DMA reserved areas under the reproduction control ofthe main controller 20 (ST126). User data recorded on the user area isreproduced on the basis of the readout defect management information(ST127).

An ECC block made up of 64 KB will be explained below with reference toFIGS. 35 to 38. One ECC block recorded on an existing DVD-RAM is made upof 32 KB. In order to realize higher-density recording than the existingDVD-RAM, an ECC block made up of 64 KB will be explained.

FIG. 35 shows the data structure of an ECC block. The ECC block is madeup of 32 successive scrambled frames. 192 rows+16 rows (columndirection) and (172+10)×2 columns (row direction) are arranged. Each ofB0, 0, B1, 0, . . . is one byte. PO and PI are error correction codes,i.e., parity data of outer-codes and parity data of inner-codes.

In the ECC block shown in FIG. 35, a (6 rows×172 bytes) unit is handledas one scrambled frame. FIG. 36 shows the scrambled frame allocationobtained by rewriting FIG. 35. That is, the ECC block is formed of 32successive scrambled frames. Furthermore, this system handles (block 182bytes×207 bytes) as a pair. If L is assigned to respective scrambledframe numbers in the left ECC block, and R is assigned to those in theright ECC block, scrambled frames are allocated, as shown in FIG. 36.That is, left and right scrambled frames alternately appear in the leftblock, and right and left scrambled frames alternately appear in theright block.

That is, the ECC block is formed of 32 successive scrambled frames.Respective rows on the left half of an odd sector are replaced by thoseon the right half. 172×2 bytes×192 rows are equal to 172 bytes×12rows×32 scrambled frames to form an information field. 16-byte PO datais appended to 172×2 columns to form outer code RS (208, 192, 17). Also,10-byte PI (RS(182, 172, 11)) data is appended to 208×2 rows of theright and left blocks. PI data is also appended to PO rows.

Numerals in frames indicate scrambled frame numbers, and suffices R andL indicate the right and left halves of the scrambled frames. PO and PIdata shown in FIG. 35 are generated in the following sequence.

Initially, a 16-byte Bi,j (i=192 to 207) is appended to column j (j=0 to171 and j=182 to 353). This Bi,j is defined by polynomial Rj(x), whichforms outer code RS (208, 192, 17) for 172×2 columns.

Next, 10-byte Bi,j (j=172 to 181 and j=354 to 363) is appended to row i(i=0 to 207). This Bi,j is defined by polynomial Ri(X), which formsinner code RS (182, 172, 11) for (208×2)/2 rows.

FIG. 37 shows the state wherein parity data of outer-codes (PO) areinterleaved to the left and right blocks in the ECC block. Bi,j aselements of a B matrix shown in FIG. 35 form 208 rows×182×2 columns.This B matrix is interleaved between neighboring rows so that Bi,j arere-allocated as Bm,n.

As a result, 16 parity rows are distributed one by one, as shown in FIG.37. That is, each of 16 parity rows is allocated for every two recordingframes. Therefore, a recording frame consisting of 12 rows has 12 rows+1row. After this row interleave, 13 rows×182 bytes are referred to as arecording frame. Therefore, the ECC block after row interleave is madeup of 32 recording frames. In one recording frame, six rows are presentin each of the right and left blocks, as described in FIG. 36. Also, POis allocated at different rows in the left block (182×208 bytes) andright block (182×208 bytes). FIG. 36 shows one complete ECC block.However, in actual data reproduction, such ECC blocks are successivelyinput to an error correction processor. In order to improve thecorrection performance of such error correction process, the interleavescheme shown in FIG. 37 is adopted.

FIG. 38 shows an example of the configuration of recorded data fields(even and odd fields). In FIG. 38, PO (Parity Out) information shown inFIG. 37 is inserted in sync data areas in the last two sync frames(i.e., portions where the last “sync code=SY3” portion and subsequent“sync data”, and “sync code=SY1” portion and subsequent “sync data” arejuxtaposed) in each of the even and odd recorded data fields.

More specifically, “part of left PO” shown in FIG. 36 is inserted in thelast two sync frames in the even recorded data field, and “part of rightPO” shown in FIG. 36 is inserted in the last two sync frames in the oddrecorded data field. As shown in FIG. 36, one ECC block is formed ofright and left “small ECC blocks”, and data of different PO groups (PObelonging to the left small ECC block or PO belonging to the right smallECC block) are alternately inserted for respective sectors.

The functions and effects of the aforementioned second defect managementmethod will be summarized below.

For example, assume that an information storage medium of the presentinvention allows up to 1000 overwrite accesses. On this informationstorage medium, registration of 10000 cases of defect managementinformation is realized. In this case, if DMAs are transited every 1000accesses, the medium can proof registration of 10000 cases of defectmanagement information by 10 (= 10000/1000) transitions in principle.That is, by allowing the DMA replacement process, poor overwritecharacteristics can be overcome.

On a conventional medium, a DMA itself does not undergo defectmanagement. For this reason, when the rewrite count of defect managementinformation becomes larger than the repetitive recordable count,satisfactory defect management is disabled in practice. For example, inthe case of an information storage medium that allows about only 1000overwrite accesses, the DMA itself is likely to be defective by 1000 ormore rewrite accesses of defect management information. Some informationstorage media in the market have poor quality. In the case of such amedium, defective blocks are formed after about only 100 overwriteaccesses. In such an inferior medium, some defects disable the wholemedium.

With the second defect management method to be summarized below, theperformance of an information storage medium that allows about only 1000overwrite accesses can be remarkably improved.

-   Target    -   Maximum OW times:100,000-   Presupposition    -   OW limitation of single DMA:1,000-   Solution    -   Plural DMAs with transition        -   Number of DMA: 100,000/1,000=100 set    -   Four identical DMAs

According to defect management of the present invention, the apparentoverwrite characteristics of a medium that allows about only 1000overwrite accesses can be improved. For example, about 100000 overwriteaccesses are allowed. This value is equivalent to the overwrite count ofa DVD-RAM. An area that has undergone 1000 overwrite accesses isreplaced by a new area. In principle, 100 (= 100000/1000) sets of DMAreserved areas need only be prepared. When a medium has 100 sets of DMAreserved areas, even a medium that allows about only 1000 overwriteaccesses can have performance equivalent to that of a medium that allowsabout 100000 overwrite accesses. The medium has, e.g., two DMA sequenceswith identical contents on the lead-in area, and two DMA sequences onthe lead-out area, i.e., a total of four DMA sequences. As a result,even when information cannot be read out from an arbitrary DMA sequence,if information can be read out from other DMA sequences, correct defectmanagement can continue. That is, a plurality of DMA sequences which canbe used at the same time are provided, and when individual DMA sequencesdeteriorate, defect management information is transferred to new DMAreserved areas. As a result, performance for protecting the DMA itselffrom failures can be improved. For example, when four DMA sequences aresimultaneously allocated on a medium, each DMA sequence has 100 DMAreserved areas. That is, a total of 400 DMA reserved areas need only beprepared on the medium.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. (canceled)
 2. An information reproduction apparatus for reproducinginformation from an information storage medium, which comprises a dataarea to store data, a plurality of defect management areas to storedefect management information used to manage defective areas on theinformation storage medium, and a current management area to storecurrent defect management area information indicating a current defectmanagement area of the defect management areas, the current managementarea located internally in the defect management areas, the currentmanagement area including reserved areas to store the current defectmanagement area information, the apparatus comprising: a reading unitconfigured to read information from the information storage medium; anda reproducing unit configured to reproduce data from the data area onthe basis of the current defect management information stored in thecurrent defect management area.
 3. An information recording apparatusfor recording information on an information storage medium, whichcomprises a data area to store data, a plurality of defect managementareas to store defect management information used to manage defectiveareas on the information storage medium, and a current management areato store current defect management area information indicating a currentdefect management area of the defect management areas, the currentmanagement area is located internally in the defect management areas,the current management area includes reserved areas to store the currentdefect management area information, the apparatus comprising: a readingunit configured to read information from the information storage medium;and a recording unit configured to record defect management informationin the defect management areas and record the current defect managementarea information in the current defect management area.